In photofinishing, customer images are printed onto a photographic paper. Conventionally this printing has been optical, using a print engine in the form of a light source which has passed through a negative to be printed, to expose the paper. More recently, it has been suggested that the exposure can be from a digitally captured image, using a print engine such as a CRT, laser or light emitting diode assembly. At wholesale photofinishing laboratories, where large numbers of images must be printed in a short time, the paper is normally supplied from a web in the form of a roll mounted within a paper dispensing cassette in a known manner. The paper cassette is light tight when closed for transport to and from the printer, and is typically loaded in a dark room to avoid undesirable fogging of the photographic paper. For convenience, the take-up cassette is of the same construction as the dispensing cassette. The only difference between the dispensing and take-up cassettes being that the dispensing cassette is pre-loaded with a roll of -photographic web mounted on an intercore, while the take-up cassette initially has an intercore which is empty. The intercores are dimensioned to fit on a motor driven rotating spindle within the printer. Rotation of the spindle can control dispensing and uptake of a paper roll. The web is exposed at a print engine in a path between the dispensing and take-up cassettes. Following exposure, the web is chemically developed in a known manner and then cut to yield paper prints of many individual images which are then supplied to respective customers.
Conventional cassettes usually have two sections, one of which swings or somehow moves with respect to the other, so as to provide a closed position which is light tight, and an open position in which a web roll mounted on an intercore can pass through the opening for mounting within the cassette. For example, one well known arrangement is the so-called "clam shell" configuration where essentially two semi-cylindrical sections are hinged at adjacent axially extending edges. Similar arrangements for film or paper canisters are disclosed, for example, in U.S. Pat. Nos. 5,482,223, U.S. Pat. Nos 5,659,833, U.S. Pat. Nos. 5,222,681, and U.S. Pat. Nos. 4,302,102. In such configurations respective mating edges of the two sections swing between a closed position in which the mating edges are adjacent to define a slit, and an open position in which they are spaced apart to allow access to the interior of the cassette. Removable clamps may be provided which are spaced apart along the mating edges, to urge the edges together and retain the cassette closed, particularly during transportation. During loading of the dispensing cassette, a leading edge of the web can be left threaded through the slit of the closed cassette. This leading edge can be used to pull the web from the cassette and thread it past the print engine and onto an empty intercore on the take-up cassette. While the clamps provide sufficient force to prevent light leakage into the cassette, they do not provide so much force as would prevent the pulling of the web through the slit.
A conventional printer which might use such cassettes will typically have a housing with two upstanding end walls, and two opposed side walls extending between the end walls. One of the side walls will typically be provided with a side door through which dispensing and take-up cassettes are passed into the housing for loading and removal from the printer. Both the dispensing and take-up cassettes must be loaded into the printer through the same door (that is, from the same side of the printer). However, during attachment of the leading end onto the intercore within the take-up cassette it is necessary to fully open the take-up cassette to allow an operator to manually perform the attaching operation. If a pair of clamps have been left engaged on the take-up cassette, the present invention realizes that to unlock the clamps it is necessary for the operator to both unlock a clamp nearest the door side of the printer, and to reach through the printer toward the opposite side in order to unlock the other clamp. This can be difficult in the confines of the spaces available within typical printers. Furthermore, the present invention recognizes that in a typical printer it is often difficult for an operator to know the direction to web feed. Thus, after installing dispensing and take-up cassettes in such a printer, it is difficult for an operator to visually distinguish the dispensing and take-up cassettes since the cassettes themselves are identical in appearance. This may lead the operator to mistakenly disengage the clamps on the dispensing cassette and open it, in the mistaken belief that it is the take-up cassette. Such a situation would lead to premature exposure of the much of the web.
The present invention recognizes then, that it would be desirable to provide a simple cassette locking arrangement which locks the mating edges at multiple positions along their lengths, yet does not require an operator to manually reach substantially inside the printer and along the cassette. The present invention further recognizes that it would be desirable if some simple means could be provided which would aid an operator in correctly identifying and opening the take-up cassette when loaded in the machine.